This invention relates to the field of control circuits for consumer appliances. More specifically, it relates to control circuits for home washing appliances, such as dishwashers and clothes washing machines. Typically, these appliances are controlled by a mechanical, electromechanical or electronic sequencer. Thus, at a selected time on a rotating drum a water solenoid is actuated to fill the washing tube, at a later time a circulate cycle is initiated to circulate the water around the clothes or the dishes, and still later a drain cycle is initiated to remove the dirty water. These basic cycles are repeated to effect washing and rinsing in a well known manner.
In the usual electromechanical sequencer it is not possible to utilize feedback information to effect subsequent system operation as, for example, where an overfill or a drain blockage occurs. In such a case the sequencer will progress through its cycles regardless of system malfunction. Thus, for example, if the drain is clogged the system will nevertheless continue filling the appliance with water even resulting in a flood condition often causing damage to the machine and surrounding structures. Additionally, if draining is effected in less time than set in the sequencer the pump motor nevertheless continues to function often leading to excessive wear.
In addition to these disadvantages resulting from the fixed nature of electromechanical sequencers there is the lack of ability to include diagnostic cycles to detect and identify machine malfunctions to facilitate repair. These devices also become unduly complicated when it is desired to include a large number of user options on the appliance as, for example, several washing, rinsing and drying cycles. The permutations of these user options can easily exceed 30 and the hard wired circuitry necessary to interface with electronic, much less electromechanical sequencers, becomes prohibitively complex and expensive.
In order to obtain an improved control circuit for washing appliances it is desired, therefore, to provide a system which can handle a large number of user options, can detect serious malfunctions and prevent flooding, can detect other malfunctions and provide diagnostic information and which can jump to the next operation cycle as soon as a drain cycle has been completed. It is accordingly an object of the present invention to provide a microprocessor based control system for a washing appliance capable of achieving these advantages.
It is an object of this invention to provide a microprocessor based control circuit for a washing appliance which includes a diagnostic capability responsive to a service technician input and which may be rapidly advanced or "stepped" through the usual operating cycle sequence to facilitate diagnosis and repair.
It is a further object of this invention to provide a diagnostic system within a microprocessor based control circuit of a washing appliance which is responsive to operator input and control for testing each operating cycle of the appliance in sequence to verify correct operation of the appliance.
It is yet another object of this invention to provide a diagnostic system in a washing appliance including a microprocessor based control circuit which utilizes the malfunction detection capabilities of the control circuit to facilitate diagnosis and repair of the appliance.
Other objects and advantages of the invention will be apparent from the remaining portion of the specification.